Method of removing finely divided solid particles from hydrocarbonaceous liquids



2 Sheets-Sheet 1 SOLVENT KULIK FROM HYDROCARBONACEOUS LIQUIDS RAW /|O TAR Jan. 27, 1959 Filed June 15. 1955 HEATING a coouue co|| s I PELLETS INVENTOR.

METRO D. KULIK m L O S TAR 8| SOLVENT BY I ATTORNEY FIG. I

Jan.-27, 1959 M. D. KULIK 2,871,181

METHOD OF REMOVING FINELY DIVIDED SOLID PARTICLES FROM HYDROCARBONACEOUS LIQUIDS Filed June 15. 1955 2 Sheets-Sheet 2 3O SOLVENT RAW TAR I MIXING VESSEL 37 38 //////n R 36 I 1 Q HEATER AGGLOMERATING CQOUNG VESSEL MEDIUM 43 TAR a SOLVENT HEATER 46 T \souo PELLETS FIG. 2

INVENTOR. METRO o. KULIK ATTORNEY United States Patent METHOD OF REMGVING FINELY DIVIDED SOLID PARTICLES FROM HYDROCARBO- NACEOUS LIQUIDS Metro D. Kulik, Pittsburgh, Pa., assignor to Consolidation Coal Company, Pittsburgh, Pa., a corporation of Pennsylvania Application June 15, 1955, Serial No. 515,647

8 Claims. (Cl. 208-45) The present invention relates to the art of removing finely divided solid particles from hydrocarbonaceous liquids. More particularly, this invention relates to a method for agglomerating finely divided particles of solid fuels which are suspended in those hydrocarbonaceous liquids derived through pyrolytic treatment of solid fuels.

The liquid products obtained by the pyrolytic treatment of solid fuels under non-quiescent conditions inherently contain substantial quantities of abrasive, finely divided solid particles of the original solid fuels. Such treatment includes, for example, low temperature, carbonization of coal, pressure extraction of coal with organic solvents, liquid phase pressure hydrogenation of coal, pyrolysis of oil shale, tar sands and the like. Where the pyrolytic degradation of solid fuels to liquid products is accompanied by considerable agitation (for example, pyrolytic treatmentby the fluidized solids processing technique), substantial quantities of the original solid fuels in extremely finely divided particulate form appear in the resulting condensed liquid product. Separation of these abrasive finely divided particles from the pyrolytically derived hydrocarbonaceous liquid cannot be accomplished by the usual mechanical separation techniques at ordinary temperatures (filtration, centrifugation, settling) because of the extremely fine state of subdivision of the solid particles and because of the high density and viscosity of the liquid. At ordinary temperatures the pyrolytically-derivcd hydrocarbonaceous liquid is not free fiowing. At the elevated temperatures required to reduce. the liquid viscosity to an operable value for the usual mechanical separation techniques, pressurized equipment is required to prevent loss of the lower boiling constituents of the liquid through volatilization. Even at these elevated temperatures (reduced viscosity), however, the usual separation techniques are inadequate since the extremely finely divided particles actually enter the interstices of conventional filtration equipment to blind the filter septum; the low density of these particles prevents their separation from the viscous liquid through settling and resists even centrifugal separation.

Throughout the present specification, these hydrocarbonaceous liquids derived through pyrolysis of solid fuels will be referred to as tars. The term pitch will refer to those tar constituents having a high boiling temperature and high fusion temperature. At ordinary temperatures, the pitch can be described as an extremely viscous liquid or as an amorphous solid.

Tars produced by low temperature carbonization of coal, for example, may contain up to 25 percent and more by weight of finely divided particles of coal or partially carbonized coal. Frequently more than 50 percent by weight of these solids will pass through a 325 mesh Tyler standard screen. The presence of these abrasive solids in the tar seriously reduces the value of the tar. Conventional processing of the solids-laden raw tar for recovery of valuable liquid constituents by conventional processing methods such as distillation or extraction. is

2,871,181 Pa'tented Jan. 27, 1959 ICC difficult. Moreover if the solids-laden tar should be refined by distillation, for example, the solids become even more concentrated in the heavy pitch remaining after the lighter, more valuable constituents have been removed. Hence the ash content of the residual pitch increases and its value correspondingly decreases.

In my co-pending U. S. patent application S. N. 406,926, filed January 29, 1954, entitled Process for Removing Finely Divided Solids from Raw Low Temperature Carbonization Coal Tars (now U. S. Patent 2,774,716) and assigned to the assignee of the present application, there is described a process for removing finely divided particles of coal and partially devolatilized coal from low temperature carbonization tars. Therein agglomerates are formed from the suspended finely divided solids on treatment of the solids-laden tar at ordinary temperatures with a tar distillate fraction capable of completely dissolving most, but not all of the liquid tar, i. e., capable of rejecting from solution a small quantity of pitch which serves as an agglomerating binder for the solids.

Subsequent work on the tars produced by those low temperature carbonization processes employing the fluidized solids processing technique has revealed thatthe finely divided solids suspended in such tars are almost universally capable of passing through a 325 mesh Tyler screen. The following Table I is a screen analysis 'of the suspended solid'particles in the tars produced by fluidized low temperature carbonization of coal and lignite.

TABLE I Screen analysis of tars produced by fluidized low temperature carbonization processes It was found that fluidized low temperature carbonization tars, which characteristically contain these extremely finely divided solid particles, could be freed of solids only at commercially unacceptable rates when treated by the process described in the above-mentioned patent application.

By the present invention, however, I am able to agglomerate even the extremely finely divided solid particles which occur in fluidizedlow temperature carbonization tars. The present invention also gives superior results when applied to other tars containing finely divided particles of the original solid fuel in a generally coarser size consist. Moreover the present invention can be applied to any solid particles in hydrocarbonaceous liquids, including the finely divided particles of carbon resulting from'thermal cracking of the tar vapors produced by high temperature carbonization in metallurgical coking ovens.

According to the present invention, the solids-laden tar isfirst mixed with a solvent in which all of the tar is substantially wholly soluble at an elevated temperature (below the initial boiling temperature of the tar and of the solvent itself), but in which a portion of the tar is insoluble at lower temperatures (above the solidification temperature of the tar). The mixture of solids-laden tar and solvent is maintained at an elevated temperature (below the incipient boiling temperature of the tar and the solvent) at which substantially all of the tar is soluble in the solvent until substantially complete solution of tar in solvent is obtained. Thereupon the mixture is maintained in continuous agitation and cooled to a reduced temperature (which is above the solidification temperature of the tar) at which a portion of pitch is precipitated from solution. The continuous agitation of the solids-laden tar and solvent during this cooling phase results in formation of spherical agglomerates consisting of the finely divided solids and droplets of precipitated pitch. The precise final temperature in the cooling phase determines the quantity of precipitated pitch and affects the average size of the resulting spherical agglomerates. Insuificient cooling precipitates insufficient pitch to bind the suspended solids. Excessive cooling precipitates excessive pitch which produces soft, tacky, cohesive agglomerates and also results in unnecessary loss of valuable liquid constituents of the tar. Thereupon the spherical pellets of agglomerated solids may be readily separated from the mixture of solvent and tar by decantation, filtration, centrifugation and the like. Preferably the separation should be effected as soon as possible after the spherical agglomerates have been formed since they tend to disintegrate upon continued contact with the tar and solvent mixture. Also it is preferable to heat the mixture of tar, solvent and agglomerated solids from the reduced temperature to an intermediate separation temperature between the reduced temperature and the elevated temperature in order to increase the solubility of the solvent to wash any sticky pitch from the surfaces of the agglomerated pellets (l) in order that they do not adhere to one another during the separation but instead retain their discrete particularity and (2) in order that excessive quantities of the valuable liquid constituents are not removed with the pellets.

To obtain extremely rapid filtration rates, the described heating and cooling cycle which I have discovered may be repeated one or more times. In such repetitive treatment the solids-laden tar and solvent are mixed and maintained at a first elevated temperature (below the initial boiling temperature of the solvent and tar) at which substantially all of the tar is wholly dissolved in the solvent. Thereupon the mixture is cooled under constant agitation to a first reduced temperature (above the solidification temperature of the tar) at which a desired fraction of pitch is rejected from solution. Thereupon the mixture is heated to a second elevated temperature which should not exceed the first elevated temperature. Thereupon the mixture is cooled to a second reduced temperature which is not lower than the first reduced temperature. If subsequent heating and cooling cycles are desired, each subsequent elevated temperature should not exceed the elevated temperature of the previous cycle and each subsequent reduced temperature should not be lower than the reduced temperature of the preceding cycle. T hereupon, from a final reduced temperature, the spherical agglomerates may be separated from the solution. Preferably the mixture is heated to an intermediate separation temperature between the final elevated temperature and the final reduced temperature. Repetition of the heating and cooling cycles as described results (a) in increased hardness and density of the spherical agglomerated particles of finely divided solids and (b) in reduced retention of liquids by the agglomerates.

The solvent which I prefer to employ in the present invention comprises at least two components: (1) a material which is an excellent solvent for the tar, and (2) a material which is a solvent for only certain portions of the tar. The two components must be wholly miscible and preferably boil entirely within the range of 50 to 300 C. In combination the components should permit total solution of the tar at an elevated temperature less than 110 C. and only partial solution at a reduced temperature above 20 C.

Examples of the solvent component of type (1) are boiling phenols; halogenated paraffins such as trichloroethylene, carbon tetrachloride, sym-tetrachloroethane; nitrogen bases such as pyridine, aniline, lutidene, quinoline; low boiling ketones such as methyl-ethyl-ketone, acetone; nitrated aromatics such as nitrobenzene; low boiling organic esters such as ethyl acetate, butyl acetate; olefins; and aromatic materials such as benzene, toluene, xylene.

Examples of materials of type (2) include paraffinic and naphthenic hydrocarbons.

The ratio of solvent materials of type (1) and type (2) for optimum results according to the present invention can be determined through routine testing with the solvent materials selected. The optimum mixture is one which is capable of rejecting from solution at a reduced temperature only that quantity of tar required to bind all the finely divided solids as an agglomerate.

While synthetically compounded solvent mixtures can be prepared for satisfactory removal of finely divided solids according to the present invention, nevertheless I prefer to employ as solvent those naturally occurring mixtures which are present and are readily recoverable from the tars themselves. I have found that neutral first distillate fractions of the tars having boiling end points up to 300 C. are themselves excellent materials for use in the present treatment. For example, a first neutral distillate fraction of low temperature carbonization tar boiling below about 200 C. is suitable. Neutral distillates are those substantially freed of phenolic components. Tar distillates from low temperature carbonization inherently contain small quantities of low boiling phenols, aromatic and olefinic hydrocarbons, which may be retained to supply a solvent component of type (1) to cooperate with the parafiinic and naphthenic hydrocarbons of type (2) inherent in low temperature carbonization tar. Slight variations in the end point temperature of the distillates can be employed to vary the solvent properties to any desired combination. It is possible to add small quantities of phenols to neutral distillates to obtain suitable solvent properties.

By employing as solvent a distillate fraction inherently contained in the solids-contaminated liquid, an extrinsic source of solvent is not required. Make-up solvent to compensate for processing losses is autogenously supplied. The total fraction of low temperature carhonization tar boiling below about 200 C., for example, usually represents from about one to about five per cent by weight of the total tar. The incremental quantity of 200 C. end point distillate contained in tar undergoing treatment is adequate to supply any processing losses which may occur; hence it is a preferred solvent for treating low temperature carbonization tars. in addition, the use of a distillate fraction boiling below 200 C. as solvent permits direct fractionation of the solids-free liquid from the present separation process into solvent and product by a single stage distillation. The distillate boiling below 200 C. comprises paraffinic and naphthenic hydrocarbons, some olefins and a small quantity (2 to 20 percent by weight) of phenols. The exact end boiling point of the solvent fraction can be correlated with the phenolic content to permit close adjustment of the solvent properties through regulation of the distillation end point.

For a clear understanding of the present invention, its objects and advantages, reference should be had to the following detailed description and the accompanying drawings in which:

Figure l is a diagrammatic illustration of apparatus for carrying out the preferred embodiment of the present invention; and

Figure 2 i a diagrammati illustration of apparatus for carrying out an alternative embodiment of the present invention.

In Figure l apparatus is illustrated for carrying out the batchwise separation of finely divided solid particles lution.

from tar contained in a vessel 10. For the purposes of this description, the process will be described for the treatment of tar resulting from fluidized low temperature carbonization of coal although it should be understood that the process applies equally well for treatment of any hydrocarbonaceous liquid derived through pyrolytic treatment of solid fuels for the removal therefrom of finely divided solid particles of the original solid fuel.

A solvent for my present invention as previously described is provided in a storage vessel 11. The solvent must be one in which the tar is substantially completely soluble at an elevated temperature (below the incipient which a portion of the tar is insoluble at a reduced temv perature (above the solidification temperature of the tar).

Raw tar is introduced from a storage vessel through a conduit 12 into a mixing vessel 13. Solvent is introduced from the storage vessel 11 through a conduit 14 into the vessel 13. Preferably the solvent to tar volume ratio is from 0.5 1 to 2.0: 1. The mixing vessel 13 preferably is an upright cylinder with a rounded bottom. A discharge conduit 15 having a valve 16 is provided for discharging material from the vessel 13. A motor driven stirring device 17 is provided in the vessel 13 to provide a whirling agitation of the contents. Means are provided for heating and cooling the vessel 13, for example, heat exchange coils 18 extending into the vessel 13 to supply heating or cooling, liquid for indirect heat exchange of the contents. If desired the walls of the vessel 13 may be jacketed to accommodate a heating medium such as steam or a cooling medium such as water.

With the motor operated stirring device 17 providing the whirling agitation to promote solution, the raw tar and solvent are maintained at an elevated temperature at which the tar is substantially wholly soluble in the solvent. This elevated temperature should be below the initial boiling temperature of the solvent and of the raw tar. When the tar is substanially completely dissolved, the solution is cooled, for example, by introducing a cooling medium into the coils 18, to a reduced tem perature below the incipient pitch precipitation temperature, but above the solidification temperature of the tar, until a small quantity of liquid pitch is rejected from so- The whirling agitation causes suspended solid particles and precipitated droplets of liquid pitch to coalesce as spherical agglomerates.

Preferably the mixture then is heated to a separation temperature which is intermediate between the elevated temperature and the reduced temperature. If the temperature is allowed to fall below the final reduced temperature, additional sticky pitch will be deposited upon the surface of the agglomerates, tending to cause them to adhere. Thereupon the valve 16 is opened and the contents of the vessel 13 are discharged through the conduit 15 to a continuous filter 20. Removal of the agglomerated solid particles by filtration is readily accomplished without danger of blinding the filter septum. The solids are recovered as a filter cake at 21. They may be used as fuel, they may be heated for recovery by volatilization of occluded solvents and tar, or may be returned to the parent pyrolysis process whence the tar was derived. Filtrate tar, free of solids, is recovered through a conduit 19 along with the solvent. A distillate fraction of the tar and solvent mixture is recovered as fresh solvent and stored in the vessel 11.

The time required for the heating and cooling steps is not critical to the operation of my present invention, so long as the suspended solids are maintained in constant agitation. When the agglomerating treatment has been completed and the suspension is in condition for filtration, the separation should be carried out as soon as possible since the spherical agglomerates tend to disintegrate into their constitutent finely divided particles if allowed to remain static in contact with the solvent. liollowing a U single cycle treatment of the tar, disintegration of the agglomerates is severe after about a half hour of static contact with the solvent. However, the tendency to disintegrate of those spherical agglomerates formed from a multiple cycle treatment is negligible. 7

To illustrate the present invention, low temperature carbonization tar containing 20 percent by weight offinely divided solids was recovered from a fluidized low temperature carbonization process. The solids in the tar had a particle size distribution shown in Table I for coal. In the following Examples 1 through 7, a quantity of the raw tar (containing solids) was mixed with an equal volume of solvent. The solvent was a neutral distillate fraction of low temperature carbonization tar having an end boiling point of about 200 C.; i. e., a 200 C. end point distillate from which all phenols had been re moved. About 2 percent by weight of phenol was thereafter added to the neutral distillate to introduce the desired solvent properties.

Example 1.--Tar and solvent were mixed at room temperature and then heated to 50 C. Filtration was attempted at 50 C. The mixture proved to be unfilterable.

Example 2.--Tar and solvent were mixed at room temperature and then heated to 70 C. Filtration was attempted at 70 C. The mixture proved to be unfilterable.

Example 3.Tar and solvent were mixed at room temperature and then heated to 100 C. The mixture was cooled to 50 C. while maintained in constant whirling agitation. I Filtration at 50 C. required seconds and produced a tacky filter cake.

Example 4.Tar and solvent were mixed at room temperature and heated to C. The mixture was cooled to 45 C. while maintained under constant whirling agitation. Thereupon the mixture was heated to 50 C. and filtered. The filtration required 27 seconds and produced a filter cake which was slightly tacky.

Example 5.Tar and solvent were mixed at room temperature and heated to 100 C. The mixture was cooled to 50 C. while maintained under constant whirling agitation. The mixture then was reheated to 100 C. and thereafter cooled to 50 C. under constant whirling agitation. Filtration at 50 C. required 10 seconds and produced a filter cake which was only slightly, tacky.

Example 6.Tar and solvent were mixed at room temperature and heated to 100 C., and thereafter, while under constant whirling agitation, cooled to 45 C., reheated to 100 C., and cooled to 50 C. Filtration at 50 C., required 6 seconds and produced a granular filter cake having no tackiness.

Example 7.--Tar and solvent were mixed at room temperature and heated to 100 C., and thereafter, while under constant whirling agitation, cooled to 45 C., heated to 98 C., cooled to 45 C., and heated to 60 C. Filtration at 60 C. required 3 seconds and produced a granular filter cake with no tackiness.

Thefilter cake produced in Example 7 had the following particle size distribution:

TABLE 11 Screen analysis for filter cake solids from Example 7 Dlfieren- Cumula- Tyler standard screen size tlal, Weight tive, weight;

percent percent 011 8 mesh 4. 5 4. 5 On 14 mesh. 32. 3 36. 8 On 28 mesh 35.0 71. 8 On 48 mesh 14. 4 86. 2 On 100 mesh. 8. 3 94. 5 On mesh- 2. 5 97.0 On 200 mesh- 0. 8 97. 8 On 325 mesh- 1. 7 99.5 Through 325 mesh 0. 5 100.0

TABLE III Analysis of filter cake solids from Example 7 Weight percent True solids 60.1

Water 10.1 Distillable tar (to 400 C.) 0.4 Solvent 5.2 Pitch (above 400 C.) 24.2

f the available liquid tar in the solids-laden feedstock used in Example 7, 91.9 percent by weight was recovered as a solids-free filtrate.

Example 8.-Lignite tar, obtained from fluidized low temperature carbonization of lignite, was mixed at room temperature with an equal volume of solvent. The solvent was a first distillate fraction of low temperature coal carbonization tar (previously freed of all. phenols) boiling entirely below 200 C. and containing about 2 percent by weight of phenol. The raw tar contained 32 percent by weight of solid material having a particle size distribution shown in Table I for lignite (100% through a 325 mesh Tyler standard screen). The mixture of tar and solvent was heated to 85 C. and there after, while under constant whirling agitation, was cooled to 35 C. and reheated to 50 C. Filtration at 50 C. was accomplished without difiiculty to yield a dry, nontacky filter cake.

Example 9.Low temperature carbonization tar containing 20 percent by weight of finely divided solid particles was recovered from a fluidized low temperature carbonization process. The solids in the tar had a particle size distribution shown in Table I for coal. The solvent employed was a distillate fraction (boiling range ISO-230 C.) of previously treated solids-free tar from the same source from which all phenols had been removed. No phenol was added. One volume of tar and one volume of solvent were mixed at room temperature and then heated to 100 C. The heating required about ten minutes. Thereafter, while maintained under constant whirling agitation by a rotating paddle stirrer, the mixture was cooled to 45 C. The cooling required about twelve minutes. Thereupon the mixture was reheated to 50 C. Filtration at 50 C. required seconds.

Example 10.-The same tar described in Example 9 was treated with a solvent comprising a distillation fraction (230 to 300 C.) of previously treated solidsfree tar derived from the same carbonization process. All phenols had been removed from the solvent. One volume of tar and one volume of solvent were mixed at room temperature and heated to 100 C. While maintained in constant whirling agitation, the mixture was cooled to 50 C. Filtration at 50 C. was attempted. This solvent proved to have too great a solubility for the tar. Insufiicient pitch rejection occurred to obtain the desired agglomeration. Filtration required 50 seconds.

As previously stated, the preferred solvent for this invention is a. distillate fraction of low temperature carbonization tar boiling in the range of 100 to 300 C. and containing 2 to percent by weight of phenols. The mixture of raw tar with 0.5 to 2 volumes of this solvent results in the desired agglomeration with initial heating of the mixture to a first elevated temperature of 75 to 110 C., followed by cooling to a temperature of 20-60 C., followed in turn by filtration at a higher any prior coolings.

temperature in the range 40 to 70 C. For extremely rapid filtration rates accompanied by minimum occlusion of tar and solvent in the pelleted solids, the heating and cooling cycle can be repeated one or more times. Thus the mixture would be heated to a first elevated temperature of to C., cooled to a first reduced temperature of 20 to 60 C., reheated to a second elevated temperature (not exceeding the first) of 75 to 110 C., cooled to a second reduced temperature (not lower than the first) of 20 to 60 C. The reheating and cooling may be repeated thereafter so long as the elevated temperature of subsequent reheating does not exceed the elevated temperature of prior beatings and the reduced temperature of subsequent coolings is not below that of Following the final cooling to a final reduced temperature, the mixture is heated to a separation temperature which is less than the final elevated temperature.

Repeated cyclic heating and cooling of the mixture of tar, solvent and agglomerated solids results in minimizing the occlusion of solvent and tar within the agglomerates formed in my present process. The agglomerates produced from multiple-cycle treatment are hard, nearly perfectly spherical and, surprisingly, of a nearly uniform particle size.

My present process also can be carried out continuously as shown in Figure 2. in both batch and continuous operation it is important that the solids during any cooling cycle be maintained in constant agitation and preferably in a whirling motion to promote formation of spheroidal agglomerates.

Raw tar from a storage vessel 30 and solvent, as previously described, from a storage vessel 31, are introduced into a mixing vessel 32 through conduits 33 and 34 respectively. The vessel 32 has sufiicient holdup capacity to assure uniform blending of the raw tar and solvent. Any suitable mixing device 35 may be employed for this purpose. The mixture of raw tar and solvent from the vessel 32 is withdrawn through a conduit 36 and heated by indirect exchange in a suitable heat transfer apparatus 37 to a first elevated temperature at which all of the liquid constituents of the raw tar are dissolved in the solvent. The heated mixture of solvent and raw tar passes through a conduit 38 to an agglomerating vessel 39. Turbulent flow of the solvent and raw tar through the conduit 36, the heat exchanger 37 and the conduit 33 should be maintained.

The agglomerating vessel 39 has a jacketed wall and preferably a rounded bottom. A cooling medium is circulated through the jacketed wall to maintain the contents of the vessel 39 at a first reduced temperature at which the desired quantity of pitch will be rejected from the solution. A solution of raw tar and suspended agglomerated solids is withdrawn from the bottom of the vessel 39 through a conduit 41 having a valve 42. The suspension may be heated in a heat exchanger 43 to the desired separation temperature and introduced through a conduit 44 to a continuous filter 45. Agglomerated solids are recovered as filter cake from the filter 45 at 46. Solidsfree tar and solvent are recovered as filtrate through a conduit 47. A distillate fraction of the tar and solvent mixture is recovered as fresh solvent and stored in the vessel 31.

If desired, the suspension of agglomerated solids in solvent and tar solution in the conduit 41 may be passed through one or more additional heating and cooling cycles to increase the hardness and density of the agglomerated solids and reduce occlusion of tar and solvent as previously described.

According to the provisions of the patent statutes, I have explained the principle, preferred construction, and mode of operation of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwisethan as specifically illustrated and described.

-- I claim:

l. The method of removing solid particles consisting essentially of finely divided particles from the class of coal and partially devolatilized coal from a hydrocarbonaceous liquid containing pitch, said liquid being derived from pyrolytic treatment of solid fuels, comprising forming a mixture of said hydrocarbonaceous liquid with a solvent boiling in the range of 50 to 300 C. and containing in wholly miscible combination type (1) materials comprising organic materials in which said hydrocarbonaceous liquids are wholly soluble at temperatures below 110". C. and type (2) materials comprising saturated hydrocarbons, said solvent having a ratio of type (1) to type (2) materials which permits substantially complete solubility of said hydrocarbonaceous liquid at an elevated temperature below 110 C. but only partial solubility at a reduced temperature above 20 C., heating said mixture to an elevated temperature below 110 C. to effect substantially complete solution of said hydrocarbonaceous liquid in said solvent, thereupon cooling said mixture under continuousagitation to a reduced temperature above 20 C. at which said hydrocarbonaceous liquid is only partially soluble in said solvent whereby a portion of said pitch is precipitated from solution for combination with said particles in agitation to form spherical agglomerates, thereupon separating from said mixture said spherical agglomerates comprising substantially all of said finely divided solid particles at a temperature which is not less than said reduced temperature.

2. The method of removing solid particles consisting essentially of finely divided particles from the class of coal and partially devolatilized coal from a hydrocarbonaceous liquid containing pitch, said pitch being derived from pyrolytic treatment of solid fuels, said particles consisting essentially of the original solid fuels, comprising forming a mixture of said hydrocarbonaceous liquid with 0.5 to 2.0 volumes of a solvent comprising a distillate fraction boiling in the range 50 to 300 C. obtained from previously treated hydrocarbonaceous liquid derived from pyrolysis of solid fuels, in which solvent said hydrocarbonaceous liquid issubstantially wholly soluble at an elevated temperature below 110 C. but only partially soluble at a reduced temperature above 20 C., maintaining said mixture at an elevated temperature below 110 C., until substantially complete solution of said hydrocarbonaceous liquid in said solvent is effected, thereupon cooling said mixture under continuous agitation to a reduced temperature above 20 C. at which said hydrocarbonaceous liquid is only partially soluble in said solvent whereby a portion of said pitch is precipitated from solution for combination with said particles in agitation to form spherical agglomerates, thereupon separating from said mixture said spherical agglomerates comprising substantially all of said finely divided solid particles at a temperature which is not less than said reduced temperature.

3. The method of removing solid particles consisting essentially of finely divided particles from the class of coal and partially devolatilized coal from a hydrocarbonaceous liquid containing pitch, said liquid being derived from pyrolytic treatment of solid fuels, comprising forming a mixture of said hydrocarbonaceous liquid with 0.5 to 2.0 volumes of a solvent comprising a distillate fraction boiling in the range 50 to 300 C. obtained C. at which a portion of said pitch .is precipitated for combination with said solidsto form spherical agglomerates of said finely divided solid particles, selecting elevated temperatures for subsequent steps not greater than that of the previous heating step and selecting reduced temperatures for subsequent steps not less than that of the previous cooling step, thereupon separating from said mixture said spherical agglomerates comprising substantially all of said finely divided solid particles at a temperature which is not less than the last of said reduced temperatures.

4. The method of removing solid particles from a hydrocarbonaceous liquid containing pitch, said liquid being derived from pyrolytic treatment of solid fuels, said particles consisting essentially of finely divided particles of the original solid fuels and capable of passing through a Tyler standard 325 mesh screen, comprising forming a mixture of said hydrocarbonaceous liquid with 0.5 to 2.0 volumes of a solvent comprising a distillate fraction boiling in the range 50 to 300 C. obtained from previously treated hydrocarbonaceous liquid derived from pyrolysis of solid fuels, in which solvent said bydrocarbonaceous liquid is substantially wholly soluble at an elevated temperature below C. but only partially soluble at a reduced temperature above 20 C., maintaining said mixture at an elevated temperature below 110 C. until substantially complete solution of said hydrocarbonaceous liquid in said solvent is effected, thereupon cooling said mixture under continuous agitation to a reduced temperature above 20 C. at which said hydrocarbonaceous liquid is only partially soluble in said solvent whereby a portion of said pitch is precipitated from solution for combination with said particles in agitation to form spherical agglomerates, and thereupon separating from said mixture said spherical agglomerates'comprising substantially all of said finely divided solid particles at a temperature which is not less than said reduced temperature.

5. The method of removing solid particles consisting essentially of finely divided particles from the class of coal and partially devolatilized coal from a hydrocarbonaceous liquid containing pitch, said liquid being derived from pyrolytic treatment of solid fuels, comprising forming a mixture of said hydrocarbonaceous liquid with 0.5 to 2.0 volumes of a solvent comprising a distillate fraction boiling in the range 50 to 300 C. obtained from previously treated hydrocarbonaceous liquid derived from pyrolysis of solid fuels, in which solvent said bydrocarbonaceous liquid is substantially wholly soluble at an elevated temperature below 110 C. but only partially soluble at a reduced temperature above 20 C., maintaining said mixture at an elevated temperature below 110 C. until substantially complete solution of said hydrocarbonaceous liquid in said solvent is effected, thereupon cooling said mixture under continuous agitation to a reduced temperature above 20 C. at which said hydrocarbonaceous liquid is only partially soluble in said solvent whereby a portion of said pitch is precipitated from solution for combination with said particles in agitation to form spherical agglomerates, thereupon separting from said mixture said spherical agglomerates comprising substantially all of said finely divided solid particles at a temperature which is not less than said reduced temperature, and recovering by distillation from the resulting solids-free liquid at least a portion of a distillate fraction thereof boiling in the range 50 to 300 C. for recycle as solvent in the present process.

6. The method of removing finely divided solid par ticles from raw low temperature carbonization tar containing pitch, said particles consisting essentially of the original solid fuels, comprising forming a mixture of said tar with 0.5 to 2.0 volumes of a solvent comprising a total first distillate fraction obtained from previously treated low temperature carbonization tar, said solvent boiling entirely below 300 C. and containing 2 to 20 percent by Weight of phenols, in which solvent said tar is wholly soluble at an elevated temperature below 110 C. but only partially soluble at a reduced temperature above 20 C. maintaining said mixture at an elevated temperature below 110 C. to elfect substantially complete solution of said tar in said solvent, thereupon cooling said mixture under constant agitation to a reduced temperature above 20 C. at which said tar is only partially soluble in said solvent whereby a portion of said pitch is precipitated from solution for combination with said particles in agitation to form spherical agglomerates, thereupon separating from said mixture said spherical agglomcrates comprising substantially all of said finely divided solid particles at a temperature which is not less than said reduced temperature, and recovering by distillation from the resulting solids-free liquid a distillate fraction thereof boiling entirely below 300 C. and containing 2 to 20 percent by weight of phenols for recycle as solvent in the present process.

7. The method of removing finely divided solid par ticles from a tar containing pitch, said tar being derived from fluidized low temperature carbonization of coal, said particles consisting essentially of finely divided particles from the class of coal and partially devolatilized coal and being capable of passing through a Tyler standard 325 mesh screen, comprising forming a mixture of said tar with 0.5 to 2.0 volumes of a solvent compris ing a distillate fraction boiling entirely in the range 50 to 300 C. obtained from previously treated tar, in which solvent said tar is substantially Wholly soluble at an ele' vated temperature below 110 C. but only partially soluble at a reduced temperature above 20 C., maintaining said mixture at an elevated temperature below 110 C. to effect substantially complete solution of said tar in said solvent, thereupon cooling said mixture under continuous agitation to a reduced temperature above 20 C. at which said tar is only partially soluble in said solvent whereby a portion of said pitch is precipitated from solution for combination with said particles in agitation to form spherica ugiornerutes, thereupon separating 12 from said mixture saidspherical agglomerates comprising substantially all of said finely divided solid particles by filtration at a temperature between said reduced temperatureand said elevated temperature.

The method of preparing hydrocarbonaceous solid agglo'merates in spherical form from finely divided solid particles of solid fuels suspended in the pitch-containing hydrocarbonaceous liquid derived from pyrolytic treatment of solid fuels, comprising forming a mixture of said hyd-roearbonaceous liquid, with a solvent comprising a distillate fraction boiling in the range 50 to 300 C. obtained from previously treated hydrocarbonaceous liquid derived t'roin the pyrolysis of solid fuels in which said hydrocarbonaceous liquid is substantially wholly soluble at an elevated temperature below 110 C., but only partially soluble at a reduced temperature above 20 C., performing sequentially at least one time. the steps of (1) heating said mixture to a first elevated temperature below 110 C., and (2) thereupon cooling said mixture under constant agitation to a reduced temperature above 20 C. whereby a portion of said pitch is rejected from solution for combination with said solids to form spherical agglomcrates of said finely divided solid particles, selecting elevated temperatures for subsequent steps not greater than that of the previous step and selecting reduced temperatures for subsequent steps not less than that of the previous step, thereupon separating from said mixture said spherical agglomeratcs comprising substantially all of said finely divided solid particles at a temperature which is not less than the last of said reduced temperatures.

References Cited in the file of this patent UNlTED STATES PATENTS 1,355,099 Weiss Oct. 20, 1920 1,722,872 Neindel July 30, 1929 2,060,447 Schoenemann Nov. 10, 1936 2,631,982, Donegan Mar. 17, 1953 2,774,716 Kulik Dec. 18, 1956 

1. THE METHOD OF REMOVING SOLID PARTICLES CONSISTING ESSENTIALLY OF FINELY DIVIDED PARTICLES FROM THE CLASS OF COAL AND PARTIALLY DEVOLATILIZED COAL FROM A HYDROCARBONACEOUS LIQUID CONTAINING PITCH, SAID LIQUID BEING DERIVED FROM PYROLYTIC TREATMENT OF SOLID FUELS, COMPRISING FORMING A MIXTURE OF SAID HYDROCARBONACEOUS LIQUID WITH A SOLVENT BOILING IN THE RANGE OF 50 TO 300'' C. AND CONTAINING IN WHOLLY MISCRIBLE COMBINATION TYPE (1) MATERIALS COMPRISING ORGANIC MATERIALS IN WHICH SAID HYDROCARBONACEOUS LIQUIDS ARE WHOLLY SOLUBLE AT TEMPERATURES BELOW 110'' C. AND TYLE (2) MATERIALS COMPRISING SATURATED HYDROCARBONS, SAID SOLVENT HAVING A RATIO OF TYPE (1) TO TYPE (2) MATERIALS WHICH PERMITS SUBSTANTIALLY COMPLETE SOLUBILITY OF SAID HYDROCARBONACEOUS LIQUID AT AN ELEVATED TEMPERATURE BELOW 110'' C. BUT ONLY PARTIAL SOLUBILITY AT A REDUCED TEMPERATURE ABOVE 20'' C. HEATING SAID MIXTURE TO AN ELEVATED TEMPERATURE BELOW 110''C. TO EFFEFT SUBSTANTIALLY COMPLETE SOLUTION OF SAID HYDROCARBONACEOUS LIQUID IN SAID SOLVENT, THEREUPON COOLING SAID MIXTURE UNDER 